title: The effect of different periods of argon deaeration on exhaled breath condensate pH.
abstract: BACKGROUND
  Exhaled breath condensate (EBC) pH has been considered as a biomarker of airway inflammation in asthma. However, little information is available on the duration of argon deaeration required to achieve a stable pH in EBC samples.
  
  
  OBJECTIVE
  To identify differences in EBC pH after argon deaeration for 2, 4, and 8 min.
  
  
  METHODS
  EBC pH was determined in EBC samples from 48 subjects with allergic rhinitis (11 asthmatics) and 14 healthy volunteers without deaeration and after argon deaeration for 2, 4, and 8 min.
  
  
  RESULTS
  The mean (95% CI) pH values obtained from samples analyzed after 4 min [7.66 (7.52-7.80)] and 8 min [7.70 (7.55-7.85)] of argon deaeration were significantly less acidic (p < .001) than those identified after 2 min of deaeration [7.53 (7.40-7.66)]; differences between pH values at 4 and 8 min were not significant. Furthermore, changes in EBC pH of nondeaerated samples after 4 and 8 min of deaeration were significantly greater than those after 2 min, the mean difference being 0.11 (95% CI, 0.02-0.20, p < .05) and 0.13 (95% CI, 0.04-0.22, p < .01), respectively; differences between changes at 4 and 8 min were not significant.
  
  
  CONCLUSIONS
  Stabilization of EBC pH is achieved after argon deaeration for 4 min. Therefore, this deaeration period may be recommended instead of the 7-8 min used in several studies.
authors.affiliation: Departamento de Medicina, Facultad de Medicina y Odontologia, Universidad de Valencia, Valencia, Spain. prieto_jes@gva.es
authors.forename: Luis
authors.initials: L
authors.lastname: Prieto
authors.forename: Belen
authors.initials: B
authors.lastname: Orosa
authors.forename: Desiree
authors.initials: D
authors.lastname: Barato
authors.forename: Julio
authors.initials: J
authors.lastname: Marin
mesh_terms: D000328:Adult; D001128:Argon / Q000008:administration & dosage*; D015415:Biomarkers / Q000032:analysis; D001944:Breath Tests / Q000379:methods*; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006967:Hypersensitivity / Q000150:complications*; D008297:Male; D012220:Rhinitis / Q000175:diagnosis* / Q000209:etiology*
chemical_list: D015415:Biomarkers; D001128:Argon